This repository showcases how Server-Sent Events can be used to power a real-time delivery tracking application. Server-Sent Events is a server push technology that can be used for real-time, one-way communication between a server and a client. Browsers can subscribe to a stream of events generated by a server using the HTML EventSource API. This is an alternative mechanism to Polling where clients make regular requests to a server with the chance that no updates have occurred. It is also an alternative to WebSockets which is a more complex real-time, two-way communication mechanism.
Example use cases where Server-Sent Events are applicable:
- Visualising real-time tracking information from IoT devices.
- Price or value updates as fluctuations occur within a market.
- News tickers with infrequent updates from live news or sports.
Below are some notable differences between Server-Sent Events and WebSockets:
| Server-Sent Events | WebSockets |
|---|---|
| Unidirectional communication between server and client | Bidirectional communication between server and client |
| Streamed over HTTP | Connects via TCP |
| Transfers textual data | Transfers textual and binary data |
While the real purpose of this repository is to demonstrate Server-Sent Events, there are some other notable tools being used that make development easier:
- pnpm for more efficient package management and quicker install speeds.
- Turborepo used to house the API and UI applications within a monorepo.
- Shared internal packages with common base files that can be overridden per application.
- Shared types between client and server enforced via Zod on both requests and responses.
- Environment variable enforcement via Zod in both API and UI applications.
These instructions assume you are running a version of NodeJS equal to or greater than the version mentioned in the .nvmrc file and have pnpm installed:
- Install dependencies across all packages and applications in the monorepo
pnpm install- Start the service and UI
pnpm dev- Run the script which simulates the truck travelling a route
./scripts/route.sh